CELTIC have crashed to league defeats three times after European ties this season - raising fears involvement in the Europa League is destroying their hopes of wresting the SPL title back from Rangers.
The worrying trend began when Neil Lennon's side suffered a shock home loss to St Johnstone three days after being held to a goal-less draw by Sion at the same venue.
They did manage to win the SPL game against St Mirren after crashing to Sion in the return leg in Switzerland.
But, defeats at Ibrox after they returned from Madrid and their serious setback at Tynecastle after the exertions of playing Udinese have raised questions about the injury- ravaged squad's ability to fight effectively on two fronts.
However, Celtic legend Bertie Auld believes that task should not be beyond them. The Lisbon Lions side he starred in were used to playing more than 60 games per season, and still sweeping all before them.
He reckons everyone in the current squad should just roll up their sleeves and accept it is just part and parcel of being at a club the size of Celtic.
Auld said: "The players have to realise Celtic is not an ordinary club, and that you must have a winning mentality to succeed here.
"Playing at home or in Europe is irrelevant, you have to go into each match believing you can win, regardless of when your last or next game will be.
"You have to give 100% every time you pull on the Celtic jersey. I don't think the players did enough to win against Hearts. But, playing in Europe a few days before is not an excuse to lose a game at the weekend."
Celtic are not only 10 points behind in the title race after dropping a third of the points available to them in the first nine games, but are also languishing in bottom spot in Europa League Group I.
Nevertheless, Auld believes no Celtic side should ever go into any competition without serious ambitions to win, and that everyone at the club should be relishing the opportunity to compete in Europe.
"I'd much rather have been playing than training during the week, and I'm sure the current players are the same," he said.
"Playing in Europe is a great honour, and I am sure the players will be enjoying it. A club like Celtic should always be competing in Europe, and I think they have performed reasonably well so far, despite the results."
What will already be worrying Lennon is that they face difficult games after each of the four remaining Europa League games.
They return from Rennes to face Aberdeen on October 23, then have away games against Motherwell, Dundee United and St Johnstone after they meet Rennes and Atletico Madrid at home and travel to Udinese for the final Group I game on December 15.
But Auld believes the boss and his backroom team can use their own extensive exper-ience of playing in Europe, then having to recover in time to play important SPL games, to ensure they succeed.
The most famous instance on their part was when they faced Boavista in the semi- final of the 2003 Uefa Cup, then flew home to beat Rangers at Ibrox.
Auld said: "The coaching staff know what it is all about. They know that teams in Europe realise how big a club Celtic are, and they want that big scalp.
"The teams in Scotland always raise their game when they come up against Celtic, and the players have to be prepared for that and deal with it.
"The have to give everything in every single match, and they have the ideal manager and coaches to help them adapt to these demands – but they have to do it quickly."